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Running Rich issue


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I've got:

1. New Cold Start injector

2. New Plugs/wire

3. New Vacumm hoses all round

4. New Fuel Injectors, new wiring harness/pigtails

I'm only getting 11 MPG -tail pipe is black and I can smell gas/fumes while I drive.

Thanks for any tips to check next

Edited by jthill3
Misspelled TItle
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Provided that the items on the list of things you replaced are all working properly, the only other things that come to mind are defective thermotime switch which would allow the cold start valve to open when it shouldn't be open, a bad temperature sensor which would keep the fuel mixthre rich beyond the temperature that it should, or a bad or improperly adjusted throttle valve switch which would not allow proper mixture compensation for the particular range (idle, after idle, full throttle).

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  • 2 weeks later...

The problem turned out to be the thermotime switch was wired backwards. This resolved both the cold start issues and my MPG improved from 11MPG to 17mpg.

No problem. The mileage could be better however. Mine rarely drops out of the 20s and that's only when I drive it hard. Most of the time it's between 23-25.5 and as much as 27.5 on long trips.
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  • 10 months later...

If I have the cold start disconnected, does my thermotime affect anything else?

also, if my temp sending unit gives a signal to my gauge, does that automatically mean it's working properly?

I'm getting <10 MPG.

neeeeed help.

also, my EGR was blocked off, so I set it up again...

and when I downshift it backfires.

I'm just super confused.

I've been reading forums and the FSM for hours.

just not quite figuring it out completely.

milage is ridiculous.

Edited by dillie327
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i was troubleshooting a similar issue where the gauge didn't work but everything else was fine and getting 20+mpg. there is another temp sensor that feeds the computer, if i remember correctly. i tested it by detaching the battery, unplugging the main big plug on the computer and checking across 2 leads (according to the FSM, id have to look that up again to be sure what pins and what values it should be between) did that for cold, then repeated for operating temp. read fine which was why it was running ok. fixed the gauge by replacing the sensor associated with it.

long answer short, there are 3 or temp related sensors.

thermotine - cold start

temp "switch" - for guage

temp sensor - for computer


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The other temp sensor is in the Air Flow Meter (AFM), called the air temperature sensor. The pins to check are described in one section of the FSM, page EF-22, and the values that they should read by temperature are in a chart on other pages, pages EF-53 and-54, along with the water temp sensor values. I don't know why they didn't just describe measuring the resistance at the ECU plug, it would make more sense, since it takes all of the connections and the sensor itself in to consideration.

I have checked mine at only two different temperatures, a fall day and a winter day, and they read correctly so I have assumed that they were good.

My car runs great, all sensors appear to work correctly, but I only get 16.5 mpg, mixed highway and short drives. I have the cold start valve fuel supply blocked, with a pressure gauge in its place, so I know it's not leaking (it was before). I haven't dug in to the tuning yet, plug reading etc., it's been too cold (which may be part of the low mpg).

The AFM resistance can be checked at the ECU plug also, page EF-52. Described for the AFM removed, but the pin numbers at the ECU are the same as on the AFM itself.

If anyone knows of a magic mileage improver, I would love to hear about. My two ton 95 Pathfinder gets better mileage.

What brand of injectors did you get (question to jthill3)? I replaced mine with new BWD injectors. I have wondered if they flow the same volumes as the stock ones.

Edited by Zed Head
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